Yeast pitching rate calculator
Under-pitching is the commonest cause of off flavours in homebrew. The cell count needed scales with volume and gravity.
billion
%
Cells needed
203.5billion
- Packs to pitch
- 3
- Packs exactly
- 2.395
- Gravity in Plato
- 13.57
- Viable cells per pack
- 85.0 billion
- Starter size for one pack
- 1.19
- Dry malt extract for the starter At 100 g per litre, which gives about 1.037 gravity.
- 119
Show the working
- Batch volume = 20
- Original gravity = 1.055
- Pitch rate = 0.75
- Cells per pack = 100
- Viability = 85
- Gravity in Plato = (-1 * 616.868) + (1111.14 * 1.055) - (630.272 * 1.055^2) + (135.997 * 1.055^3) = 13.5695
- Cells needed = 0.75 * 20 * 1000 * 13.5695 / 1000 = 203.543
- Viable cells per pack = 100 * 85/100 = 85
- Packs exactly = 85 > 0 ? 203.543 / 85 : 0 = 2.394 62
- Packs to pitch = ceil(2.394 62) = 3
- shortfall = max(203.543 - 85, 0) = 118.543
- Starter size for one pack = 118.543 > 0 ? 118.543 / 100 : 0 = 1.185 43
- Dry malt extract for the starter = 1.185 43 * 100 = 118.543
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
Scenarios & local history
Compare a saved scenario
Recent calculations
The formula
- cells = pitch rate x volume in mL x degrees Plato
- Plato is derived from specific gravity by the standard cubic fit
Liquid yeast loses roughly 20% viability a month in the fridge. The date on the pack matters.
Lagers need twice the pitch of ales because they ferment cold and the yeast reproduces slowly.